Numerous analytical methods have been developed for determining the presence or absence and/or quantifying the amount of various analytes in tissues and fluids of organisms. Currently most diagnostic testing is done with blood, urine, fecal material, or tissue biopsy. Testing based on these materials, however, entails substantial invasion of privacy and poses a significant safety hazard (particularly with the testing of blood). In contrast, the collection of oral fluid including saliva and/or mucosal transudate for testing entails relatively little invasion of privacy, is relatively safe, and can be accomplished rapidly with relative ease.
The use of oral fluid for detection purposes has been discussed in scientific and clinical research for some time. A multitude of researchers have investigated using oral fluid as a possible clinical specimen for diagnosis of specific disease states or altered metabolic activity (see, e.g., Ann. New York Acad. Sci., Vol. 694: Saliva as a Diagnostic Fluid, Malamud and Tabak, eds., N.Y. Acad. Sci. Pub. (1993)). There is a preponderance of evidence that suggests that oral fluids might be extremely useful samples for the detection of certain analytes. The basic technological premise is that analytes present in blood will pass through the oral mucosa and/or salivary glands into the oral cavity where they can be detected. Further it is assumed that the concentration of analyte in oral fluid will be indicative of the blood concentration. There is thus considerable interest in the development of devices for the collection, transport, and sample handling of oral fluids and in the development of oral fluid-based assays; in particular assays for various antibodies and metabolites.
Typically in tests performed with samples such as blood, urine, or fecal material, there is an ample supply of test material and high volumes of analytes are available for assay. In addition, since assays of such materials are performed outside the body, there is no issue of contamination of the body with assay reagents.
This is illustrated, for example, in the assay device described by de Zoeten et al., U.S. Pat. No. 5,611,995, issued Mar. 18, 1997. In this device an absorbing body is supplied with a handle and held in the stream of urine being expelled from the body. When the absorbing body is saturated, it is then inserted into a holding device having a test strip. The saturated pad comes into contact with a test strip, is compressed, and deposits urine to be tested on the test strip. A gap at the side of the hold device holding the test strip assures evaporation of excess fluid to prevent backflow along the test strip.
Previously described assays of biological samples, in particular assays for analytes in oral fluid, have typically required at least two different actions. First the sample, e.g., blood, or urine is collected. Then the collected sample is either stored, e.g., for later assay in a laboratory, or is assayed in or by an assay device which is typically a device other than the collection device. Such assays, requiring multiple components, are often expensive to manufacture and cumbersome for home use.
Moreover, particularly with respect to assaying oral fluid samples, oral fluid is often in short supply, particularly under circumstances where the test subject is stressed (e.g., when testing for drugs of abuse or life-threatening illnesses, which may make it difficult to use such multi-component assays).
When typical absorbent pads are used to recover oral fluid, the pads must typically be compressed to release the trapped oral fluid. The manipulations associated with the compression step can result in sample contamination. In addition, such a traditional pads have a significant void volume requiring that the sample often be collected in a volume significant greater than is actually required for analyte assay itself.